1. Field of the Invention
The present invention relates to a mold core positioning device that is operable to position a core member in a mold cavity defined by a pair of moveable mold segments. More particularly, the present invention relates to a mold core positioning device that operates automatically to extend a core member into a mold cavity as the mold is closed, and to retract the core member from the mold cavity as the mold is opened.
2. Description of the Related Art
Core members of various types and configurations are provided in mold constructions to form apertures, recesses, and the like, in molded parts. Typically, core members extend fully or partially into a mold cavity to help define the final geometry of the molded part. In some mold constructions, the core members remain stationary with respect to the mold cavity throughout the molding cycle. Alternatively, a mold can include a core member that is movable with respect to the cavity to enable the formation of elements that are not compatible with the direction of mold separation. These movable cores can be positioned by a dedicated actuator or they can be configured as to automatically insert and retract a core member relative to a mold cavity at an appropriate time in the molding cycle.
One form of automatically operated mold core positioning apparatus is disclosed in U.S. Pat. No. 3,060,509, which issued on Oct. 30, 1962, to J. T. McCubbins, Jr. That apparatus includes a plurality of core pins that are adapted to be inserted automatically into and to be withdrawn from the mold cavity. Each core pin is carried in a first mold portion and has an engaging shank that includes grooves that are engageable by a respective slide member. The slide members include first and second inclined cam surfaces that are received in and are engageable with the shank grooves. The slide members are carried by a second mold portion and are moved relative to the grooves in the engaging shanks as the mold portions are moved into engagement to selectively move the core pins into the mold cavity as the mold closes, and also to retract the core pins from the mold cavity after the molding material has been injected into the mold cavity, allowed to cool, and the mold is opened. The slide members are spring biased so that when the mold segments separate, the springs urging the slide bars in a direction to cause the core pins to be retracted from the mold cavity, to thereby enable the molded part to be withdrawn from the mold.
Although the McCubbins, Jr. device is operable to control automatically the movement of the core pins, it has a complicated structure that requires considerable machining of each of the mold segments in order to properly accommodate the springs, the slide bars, and the associated slide members. Additionally, the device as disclosed operates to provide a sudden and continuing constant retraction force to the core pin throughout the retraction phase of the molding cycle, and a substantially constant extension force during the core pin extension phase of the molding cycle.